>From New Scientist, 30 January 1999
Can we really stomach GM foods?
Gut reaction
Debora MacKenzie
Fears that genes for antibiotic resistance could
jump from genetically modified foods to bacteria in
the gut may be fuelled by new research from the
Netherlands. The results show that DNA lingers in the
intestine, and confirm that genetically modified
bacteria can transfer their antibiotic-resistance genes
to bacteria in the gut.
Using an "artificial gut", the Dutch researchers
showed that DNA remains intact for several minutes
in the large intestine. "It was a surprise to see that
DNA persisted so long in the colon," says Hub Noteborn of
the State Institute for Quality Control of Agricultural
Products in Wageningen, who helped organise the research.
One concern about some genetically modified (GM) crops,
such as maize used as animal fodder, is that they include
a gene for antibiotic resistance. The resistance genes are
used to track the uptake of modified genes, and are not
expressed in the crops.
While some scientists fear that these genes could jump into
bacteria in the guts of livestock and create antibiotic-
resistant pathogens, others have said there is no such risk
because the modified DNA breaksdown quickly. The Dutch
results cast doubt on these assurances, Noteborn says.
The computer-controlled artificial gut, dubbed TIM, was
designed by Robert Havenaar and his colleagues at the TNO
Nutrition and Food Research Institute in Zeist to mimic the
digestion of food. It provides a mechanical model of the
stomach and intestines, and contains the normal microbes and
enzymes in the gut.
When TIM was used to study the effects of digestion on
bacteria engineered to contain antibiotic-resistance genes,
Havenaar found that DNA from the bacteria had a half-life of
6 minutes in the large intestine. "This makes it available
to transform cells," he says.
If the modified bacteria were a type normally found in the
gut, such as Enterococcus, the experiment showed each had a
1 in 10 million chance of passing DNA containing antibiotic
resistance genes to an indigenous gut bacterium when they
came in contact.
There are normally around a thousand billion gut bacteria,
suggesting many would be transformed. If some normal gut
inhabitants were killed off--as in the guts of people or
animals on antibiotics--the transfer rate from gut-type
bacteria increased tenfold. "This is the first time the rate
has been measured," says Noteborn.
Bacteria not normally in the gut, such as Lactobacillus,
did not transfer antibiotic-resistance genes to a normal
population of gut bacteria at a detectable level, according
to a TNO internal report.
Nor did the Flavr Savr tomato, engineered by the California
based company Calgene to resist rot, although up to 10 per
cent of its DNA reached the colon. The researchers hope to
carry out the crucial test of whether foreign bacteria and
GM foods transfer their genes when gut microbes are
depleted. "We plan to ask the European Union to fund
further research," says Havenaar.
Finding the answers could resolve a long-standing debate.
In Britain, a report from the House of Lords select
committee for the European Communities last week judged it
"extremely unlikely" that genes introduced into edible
crops
migrate into gut bacteria.
But the new findings show more research is essential, says
Derek Burke, former chair of Britain's Advisory Committee
on Novel Foods and Processes. "We can only say that the risk
is not zero," he says. "Anything that would help put numbers
on this, would be useful."
Despite its confidence that genes are unlikely to jump from
GM foods, the Lords' report called for the use of antibiotic
-resistance genes "to be phased out as quickly as possible".
But in the US, maize carrying these genes will continue to
be harvested,mainly for cattle feed.
New Scientist this week (30th Jan 1999 p. 4) has
a review of some research from the Netherlands.Results of the studies
indicate that genes for antibiotic resistance could jump from genetically
modified foods to bacteria in the gut.New scientist is available on-line at <A
href="http://www.newscientist.com">www.newscientist.com
Resent-Date: 7 Feb 1999 01:07:30 -0000
From: "Dorothy Bowes" <asehaqld@powerup.com.au>
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